I just got a new toy the other day... Glock 22 .40 S&W and a safariland ALS holster... HOLY CRAP!!! It's soooooooo much better than the serpa... WOW is it better than the serpa. I will say, I agree that the serpa seems more secure for the paddle, but the draw is 1000x better with the ALS... only thing I'm not liking is the cant of the holster.. but that actually might be more the angle of the glock handle.
I also think it's a lot less obvious as to how it works if anyone happened to try to grab it, additionally, it doesn't have the opportunity for jamming like the serpa due to the release placement.